Direct carotid-cavernous fistulas are high-flow shunts with a direct connection between the internal carotid artery and the cavernous sinus. The goals of treatment are to eliminate the fistula and preserve carotid artery patency. The authors reviewed the outcome of 98 patients with 100 consecutive direct carotid-cavernous fistulas initially treated by transarterial embolization with detachable balloons (1979-1992) at the University of Cincinnati Medical Center to evaluate the merits of this technique and to provide a standard for comparison with future treatment alternatives. Among 100 fistulas, 76 were traumatic in origin, 22 resulted from a ruptured aneurysm, and 2 were iatrogenic. The most common presentations were orbital bruit (80%), proptosis (72%), chemosis (55%), abducens palsy (49%), and conjunctival injection (44%). Eighty-eight fistulas were successfully occluded in 86 patients with detachable balloon(s), and internal carotid blood flow was preserved in 66 patients (75%). Initial attempts at balloon occlusion failed in four patients in whom the fistula eventually closed spontaneously. Five patients required direct surgery to occlude the fistula, and two were treated with nondetachable balloons; one patient died from injuries sustained from trauma. The permanent neurological complication rate was 4%, including cerebral infarction in one patient, frontal intracerebral hemorrhage in one patient, and vision loss in another patient. One death occurred related to cerebral infarction from a balloon that shifted. Transient ischemia occurred in three patients. On the basis of these results, we conclude that transarterial embolization with detachable balloons provides a high rate of fistula obliteration with low morbidity and is the best initial procedure to treat direct carotid-cavernous fistulas.